1. Field of the Invention
The present invention is related to an apparatus and method for image processing, in particular, to an image processor adaptive to a plurality of coding and decoding procedures.
2. Description of the Related Art
The JPEG (Joint Photographic Expert Group) algorithm, which uses a discrete cosine transform (DCT), is one of the most common static image compressing methods. The JPEG algorithm achieves high compression with reduced image deterioration, and thereby allows personal computers and facsimiles to process image data with reduced hardware resources.
The JPEG algorithm, however, suffers from several drawbacks, including image deterioration at low bit rates.
In order to overcome these drawbacks, JPEG 2000 algorithm has been recently standardized and become commercially available. The JPEG 2000 algorithm employs a discrete wavelet transform (DWT) to code and decode image data in place of the discrete cosine transform.
This situation requires image processing apparatuses to support both of the conventional JPEG and JPEG 2000 algorithms. Japanese Unexamined Patent Application No. 2001-103484 discloses an image processing apparatus selectively performing the DCT and DWT to be adaptive to the conventional JPEG and JPEG 2000 algorithms. FIG. 1 shows a block diagram of the disclosed image processing apparatus. The disclosed image processing apparatus is composed of an input selector 50, a DCT processor 51, a DWT processor 52, and an output selector 53. The input selector 50 selects one of the DCT processor 51, the DWT processor 52 in response to a selection signal received from a circuit, and transfers input data to the selected processor. The DCT processor 51 encodes the data received from the input selector 50 using the discrete cosine transform, while the DWT processor 52 encodes the data received from the input selector 50 using the discrete wavelet transform. The output selector 53 outputs the encoded data in response to the selector signal.
Japanese Unexamined Patent Application No. H06-46404 discloses an image data processing apparatus for reducing image derogation in image edges. This image data processing apparatus detects image edges in units of image blocks, and encodes the image block(s) including the detected image edge(s) using the wavelet transform in place of the discrete cosine transform.
An issue of the conventional image processing apparatuses is that they requires large hardware resources to support both the DCT and DWT algorithms.
A need exists to provide an image processing apparatus which supports both the DCT and DWT algorithms with reduced hardware resources.